Currently, there is a need to preserve natural resources and reduce dependence on landfills and similar waste storage facilities. To meet this need, several processes and machines are used to identify and sort waste materials, such as glass. Glass containers and other glass objects are recycled by first crushing or breaking the glass into glass cullets, which are small pieces of glass of varying characteristics that are distinguished by color. Prior to recycling, glass cullets of varying colors such as clear, green and brown, as well as combinations are placed on a conveyer belt and need to be separated and sorted.
U.S. Pat. No. 5,314,071 to Christian et al. teaches a method of purification and color sorting of waste glass as well as, a glass beneficiation process and apparatus. Christian et al. teach a method of sorting glass based on the transmission properties of the glass using red and green lamps. In addition, Christian et al. detail a method of using an actuator to deflect the trajectory of the glass. The deflection causes the glass to descend into one of two paths, which is the undeflected trajectory and the deflected trajectory. The specifics of the prior sorting system is taught and described in U.S. Pat. No. 5,314,071 to Christian et. al, which is hereby incorporated by reference.
As full scale beneficiation has become more prevalent, the disadvantages of the system and method taught in Christian et al. have been realized. First, the red and green lamps taught in Christian et al. limit the spectral response of the system. Glass entering the beneficiation plants contain shades of green, brown or blue that cannot be differentiated with a red and green lamp. The second disadvantage by the system taught in Christian et al., is that Christian et al. describe a means to deflect the trajectory of the descending glass with a single actuator, which is termed a binary sort. Therefore, the single actuator in Christian et al. performs several sorting stages to arrive at a pure material. Additional sorting stages add cost, energy and time to the equipment and sorting process.
A system and process which overcomes the limited spectral response equated with the red and green lamps is desirable. A system and process which utilizes multi stage sorting to increase the efficiency of the sorting system is also desirable.